Tuna

Tuna are incredible fish. They're big – weighing up to 700 kilos. And they're fast – accelerating faster than a sports car. They can dive 250 metres in less than a minute. They can sell for millions of dollars for just one fish. They are the central part of the diet of millions of people (and cats!). And they are running out.

Tuna are kings in the ocean. Their silver scales glint as they speed through the water. They are top predators and can make short work of other shoals of fish when it comes time for feeding. The majestic bluefin's value is astronomical. In January 2013 a single fish, weighing 222 kilograms, sold at Japan’s fish market for a staggering $1.8 million dollars.

Tuna can travel thousands of kilometres in their lifetime, but they can't outrun the fishing boats any more, unless we can give them ocean sanctuaries where they can have time to recover their numbers.

The increasing demand for the world's favourite fish gives no incentive to scale back the rampant overfishing. Nor are tuna the only victims – sharks, turtles, seabirds and other marine life are casualties of some of the giant nets and many thousands of hooks out there hunting down tuna. There are techniques that aren't so damaging – like the pole and line method. Many fishermen are making a good and, crucially, sustainable business out of operating in this way.

If we change our buying habits and support sustainable fishing practises like this, we can change the story of tuna.

Where have all the tuna gone?

Tuna is not just one type of fish – there are many species of varying colour and size, widely distributed across the oceans of the world. There are seven important commercial species of tuna and many more smaller related species. However, our appetite for tuna – for sandwiches and sushi – is pushing some species of the fish closer and closer to commercial extinction.

Populations of all three species of the magnificent bluefin tunas, the most iconic and commercially valuable of all tuna species, are on the brink of collapse. Atlantic bluefin is listed on the IUCN Red List of Threatened Species as Endangered and southern bluefin as Critically Endangered. Pacific bluefin has less than 5%, of its population left, similar to southern bluefin. And yet we keep fishing them!

The last and most plentiful of the big seven – skipjack – is caught more than any other type of tuna. It's the one most likely to end up in catfood and cans.

While skipjack is not yet overfished, if the current rate of catch continues it will be. In addition, the methods used to net skipjack all too often catch young yellowfin and bigeye as well, threatening these species further.

More tuna trouble

Numerous other marine species are hooked and netted across the oceans in the hunt for tuna. More than 100 million sharks, and tens of thousands of turtles are killed every year as bycatch.

And as with all fishing fleets, advances in technology mean bigger and bigger ships – floating tuna factories – are now able to take as much tuna in two days as some countries can take in a year.

Of course the pirate fishing fleets are always on standby to steal from any countries waters. Often they transfer their illegal catch far out at sea into "legal" processing boats, effectively laundering their stolen fish and making it almost impossible to trace. We can easily stop this practise by banning the transfer of fish at sea and insisting boats come into port, where the catch can be checked and verified.

Some legal fishing companies are almost as bad as the pirates when it comes to tuna. A "sweetheart deal" sounds like something you would want – right? Not in this case. It means countries and rich multinationals offering a fraction of the value of the tuna catch in return for licenses to fish in the waters of coastal states. Sometimes they pay as little as five percent of the value of the fish. It's just wrong.

So how can we put it right?

The first part of the answer is always cut down the number of boats on the water – starting with the biggest and baddest. There are simply too many boats chasing too few fish. Make sure those remaining are using methods that don’t have bycatch issues – like pole and line.

Secondly – create oceans sanctuaries. We need to protect the tuna populations that are left, and give them time to recover. A network of sanctuaries across 40 percent the world's oceans will give all marine species that healing time. Strategically placed sanctuaries that defend the breeding and spawning grounds of the tuna will bring a new generation of the kings of the sea.

The last part of the answer is always in your hands. Don't buy endangered tuna. Don't let your local supermarket or restaurant sell it. If you see tuna in a tin or on a menu, ask where it came from and how it was caught. If you can’t be sure it was caught well, from healthy stocks – then don't buy it. Save this page in your smartphone if you have one – and show your local retailers this story.